For a variety of applications, equipment and component designers are finding uses for ceramic, intermetallic, and metallic composites. One reason for this trend is that the ability of composite materials to withstand high temperature stresses as structural elements is greatly desired. However, the ceramic and intermetallic composites typically may fracture under the strain of use due to brittleness and tend to creep at high temperature. As a result, these materials are not entirely suitable for structural components in numerous applications.
Some known attempts to overcome the brittleness and creep problems use fibers or whiskers to reinforce the ceramic and intermetallic composites. For example, in one effort a MoSi.sub.2 matrix was reinforced with 20 volume percent SiC whiskers to achieve a 54% increase in the fracture toughness and a 100% increase in the flexural strength of the material. In this effort, the fracture toughness of 8.2 MPa.m.sup.1/2 was obtained. Although this represents a significant improvement in the material properties of the composite material, the fracture toughness still falls short of the acceptable regime for structural components in most applications. In many structural component applications, a consistent fracture toughness level of 12-15 MPa.m.sup.1/2 is desirable. As a result, significant room for improvement exists in the fracture toughness of composite materials. Additionally, known applications of whisker impregnated composite materials still exhibit considerable creep at high temperatures under load.
Thus there is a need for a composite material that does not exhibit the brittleness of known ceramic, intermetallic, and metallic composites.
There is a need for a composite for use in structural components that possesses improved fracture toughness.
There is yet the need for a ceramic and intermetallic composite that advantageously uses whiskers for increased flexural strength, as well as further providing increased fracture toughness beyond known levels.
There is furthermore the need for an improved composite material that avoids the high temperature creep phenomenon of known composites.